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Paul Workman · 12-08-2008

I started this response and then got called away, and didn't have time to read all the responses. So, at the risk of being redundant...

One of the classic failure modes of electronic stuff is due to heat fluctuations; usually failing when going from cold to hot (but not always). Since it worked normally for a while and then quit, my focus would be on the regulator at this point: either it is failing, or there is a connection associated with the alt that is intermittent.

The regulator varies a DC pulse width to the stator, thus maintaining the DC voltage to the "load". IF the regulator is breaking down when hot, OR the plug-in connector on the back of the alternator (or some other) is intermittent, then the regulator will not increase the stator current pulse width - especially at low speed - and the DC voltage "falls out of regulation".

RE That connection that drives/supplies the regulator: It is a connector on the back of the alternator, and if it is loose/corroded, the alternator output can be low, or erratic as hell, depending on the nature of the contacts. (I tried all my tricks to enlarge this schematic (from the FSM), but you'll probably have to save it and look at it outside this post to better see it.)

__________________

All That Said... Now I'll tell ya what really intrigues me...That surging! The video shows the voltage fluctuations are in coincidence with an idle surging - not the surge as much as when the rpm falls off is when the voltage drops "out of regulation". My point is, there is a chance it is not the regulator or the alternator per se', but a combination of the rpm surging/fall off that is coincident with the voltage dropping out of regulation at low rpm (a FACT we see in the video clip...a very helpful video clip too, I might add!), aggravated by the under-driven alternator!?

Bottom line: I'd try to eliminate a few things first-

First I'd want to eliminate that surging at idle (usually due to an air (vacuum) leak). That eliminated, see what the alternator voltage does. If the surging is eliminated and the voltage is still out of regulation (assuming idle is 700 rpm or better), then I'd be considering putting the stock pulley back on the alt and see what that does.
Then, with those two items eliminated, if the regulator isn't regulating, then I'd be checking that connector plug on the back of the alt to be sure all is clean there.
With a faulty connection being eliminated...now you're down to the regulator itself. Time to pull that alternator and swap regulators (with a quality one this time) as re-builders don't always use "the good stuff".

Good luck my man!

P.

12-08-2008	#14
Paul Workman Join Date: Nov 2007 Location: Squires (near Ava MO in the Mark Twain N'tl Forest) - Missouri Posts: 6,466	Re: Charging system Problem ! I started this response and then got called away, and didn't have time to read all the responses. So, at the risk of being redundant... One of the classic failure modes of electronic stuff is due to heat fluctuations; usually failing when going from cold to hot (but not always). Since it worked normally for a while and then quit, my focus would be on the regulator at this point: either it is failing, or there is a connection associated with the alt that is intermittent. The regulator varies a DC pulse width to the stator, thus maintaining the DC voltage to the "load". IF the regulator is breaking down when hot, OR the plug-in connector on the back of the alternator (or some other) is intermittent, then the regulator will not increase the stator current pulse width - especially at low speed - and the DC voltage "falls out of regulation". RE That connection that drives/supplies the regulator: It is a connector on the back of the alternator, and if it is loose/corroded, the alternator output can be low, or erratic as hell, depending on the nature of the contacts. (I tried all my tricks to enlarge this schematic (from the FSM), but you'll probably have to save it and look at it outside this post to better see it.) __________________ All That Said... Now I'll tell ya what really intrigues me...That surging! The video shows the voltage fluctuations are in coincidence with an idle surging - not the surge as much as when the rpm falls off is when the voltage drops "out of regulation". My point is, there is a chance it is not the regulator or the alternator per se', but a combination of the rpm surging/fall off that is coincident with the voltage dropping out of regulation at low rpm (a FACT we see in the video clip...a very helpful video clip too, I might add!), aggravated by the under-driven alternator!? Bottom line: I'd try to eliminate a few things first- First I'd want to eliminate that surging at idle (usually due to an air (vacuum) leak). That eliminated, see what the alternator voltage does. If the surging is eliminated and the voltage is still out of regulation (assuming idle is 700 rpm or better), then I'd be considering putting the stock pulley back on the alt and see what that does. Then, with those two items eliminated, if the regulator isn't regulating, then I'd be checking that connector plug on the back of the alt to be sure all is clean there. With a faulty connection being eliminated...now you're down to the regulator itself. Time to pull that alternator and swap regulators (with a quality one this time) as re-builders don't always use "the good stuff". Good luck my man! P.